Process for the production of nitroarenes with high para-selectivity from monosubstituted aromatic hydrocarbons using alumino-silicates as catalysts

Abstract

The present invention relates to a process for the production of nitroarenes with high para-selectivity from monosubstituted aromatic hydrocarbons using aluminosilicates as catalysts, which comprises nitration of monosubstituted aromatic hydrocarbons using aluminosilicates of different ratios wherein Si/Al ranges between 5 to 1000 and the said aluminosilicates being manifested in the form of variety of zeolites and K10 montmorillonite as catalysts using nitric acid in the molar ratio of nitric acid to monosubstituted aromatic hydrocarbons ranging between 0.25 to 2.5 at a temperature in the range of 30-160 DEG C. for a period ranging between 0.25 to 3.0 h and followed by continuous removal of water formed from the reaction mixture with a Dean-Stark apparatus and recovery of the product mixture by concentration of the reaction mixture after separation of the catalyst by filtration.

We claim: 
     
       1. A process for the production of nitroarenes with high para selectivity from monosubstituted aromatic hydrocarbons using aluminosilicates as catalysts, which comprises nitration of monosubstituted aromatic hydrocarbons using beta zeolite with Si/Al of from 15 to 22 as catalyst using nitric acid as nitrating agent with azeotropic removal of water formed and present in the reaction mixture. 
     
     
       2. A process as claimed in claim 1 wherein nitric acid was used as the nitrating agent and the molar ratio of nitric acid to aromatics ranging between 0.5 to 2.5. 
     
     
       3. A process as claimed in claim 1 wherein nitric acid was used as the nitrating agent in the concentration ranging from 60 to 70%. 
     
     
       4. A process as claimed in claim 1 wherein monosubstituted aromatic hydrocarbons used are selected from toluene, ethylbenzene, cumene, anisole, chlorobenzene, bromobenzene and lodobenzene. 
     
     
       5. A process as claimed in claim 1 wherein nitration is effected at a temperature in the range of 30 to 160° C. 
     
     
       6. A process as clamed in claim 1 wherein the reaction time of nitration is effected in the range of 0.25 to 3.0 h. 
     
     
       7. A process as claimed in claim 1 wherein the product ratio for ortho:meta:para ranges from 29.4:2.3:65.7 to 5.4:6.5:36.4 depending upon the catalyst used. 
     
     
       8. A process as claimed in claim 1 wherein the product ratio for ortho:meta:para ranges from 13:0:87 to 25:0:73 depending upon the substrate used. 
     
     
       9. A process as claimed in claim 1 wherein selectivity of p-isomer increases to the extent of 5-10% with the increase of catalyst amount. 
     
     
       10. A process as claimed in claim 1 which is carried out in the absence of sulfuric acid. 
     
     
       11. A process as claimed in claim 1 wherein the catalyst not only imparts high activity by the presence of acidic sites but also high para selectivity due to the restricted dimensional configuration of the catalysts. 
     
     
       12. A process as claimed in claim 1 wherein the solid acid catalysts used here act as bifunctional catalysts, generating electrophile, nitronium ion as well as instant adsorbent for water formed during the reaction to facilitate electrophilic substitution on arenes. 
     
     
       13. A process as claimed in claim 1 wherein nitration is effected by continuous azeotropical removal of water present in the nitric acid and formed from the reaction mixture with Dean-Stark apparatus using substrate as self solvent or chlorhydrocarbons as solvent to regenerate active sites of the catalyst generating nitronium ions. 
     
     
       14. A process as claimed in claim 1 wherein recovery of nitroarenes is carried out by separating the catalyst by filtration and removing the excess aromatic hydrocarbons by distillation or by concentration in rotavapor.